Most recording techniques are easy enough to put into practice when you're only faced with the task of working with one instrument or voice at a time, but life gets more complicated when you come to record a rock band playing 'live' in the studio. The main problem in this scenario is spill, specifically from the louder instruments to the mics used on quieter sound sources. In a typical guitar-based rock band, the most vulnerable mics are those used by vocalists and the drum overheads, but acoustic instruments such as acoustic guitars or hand percussion can also present challenges.
Spill can be reduced by the careful setting up of the microphones and sound sources, though in a small studio you'll never get rid of it entirely, not even if you put up acoustic screens. There may also be other problems, such as snare drums resonating and buzzing along with the bass guitar part where, even though you can gate the close snare-mic to get rid of it there, some buzzing may still be audible in the overhead mics. Fortunately, some drum-kit rattle and buzz currently seems acceptable as part of the natural sound of the kit, whereas, for example, in the '80s it was fashionable to try to keep the kit sounding as clean and sterile as possible.
Let's assume that you have the entire band set up in a lounge-sized room. What can you do to cut down on spill? Guitar amplifiers are obvious culprits, and rock guitarists still seem to like to have big amps turned well up. For recording, though, a small amp cranked hard will often give you a much bigger sound than a stage amp used in a confined space. I'm currently using one of the little Vox AD30VTs for recording, as they sound good at just about any level, but small tube amps such as the Fender Blues Junior are also ideal: if all those early Led Zeppelin tracks were recorded using a 6W tube amp, small amps have to be OK! Where you must use a high-powered stage amplifier, particularly a tube model, I'd seriously recommend investing in a good power soak to plug between the power amp and speaker, so that you can run the power amp hard while attenuating the amount of power reaching the speaker. Even five watts can sound pretty loud in a small room, so choose a model with switchable attenuation settings, such as the THD Hot Plate (see SOS June 2006 for more about power soaks).
You're only going to put the mic in front of one speaker, so using a 4 x 12 cabinet isn't really necessary unless you're recording in a very large space, where you can also make use of a distant mic to augment the sound. In a typical project or home studio, it is pretty universally accepted wisdom that you put the mic fairly close in, in front of the best-sounding speaker — though using a smaller cabinet with a single speaker might give you just as good a sound, while also reducing spill. As regular readers will already know, the choice of mic and its position across the front of the speaker cone have a dramatic effect on the sound you ultimately capture, so try everything you have and make notes on what works. My personal favourites from my own mic collection are an SE ribbon mic and an Audio Technica AT4050 capacitor mic, though many engineers still swear by the Shure SM57 dynamic mic. There are no real rules and every combination will sound different, so please take the time to try a few different options. Getting the right sound at source is invariably better than struggling with EQ after you've made the recording.
There are various strategies that can really help reduce spill from guitar amplifiers, one of which is to point the guitar amplifiers (this is simpler with closed-back models) away from the drum kit and other vulnerable mics, and to place a thick sound-absorber a couple of feet in front of the amplifier to soak up some of the sound once it has gone past the microphone (which will usually be no more than six inches from the speaker grille cloth). We've tried mattresses, soft furnishing such as sofas, heavy folded blankets and, of course, folded duvets. They all help, but there'll still be some spill. With open-backed amplifiers, it is worth experimenting by pointing the side of the amplifier towards vulnerable mics, as open-backed cabinets have a modified dipole (figure-of-eight) polar pattern, which means that more sound comes out of the front and back than out of the sides. This time you may wish to improvise sound absorbers between the amp and the other vulnerable mics in the room, as well as behind the microphone.
If you think something might work, don't be afraid to give it a try: you might just stumble across something really effective. If you're recording in your living room, for example, try sticking the guitar amps behind the sofa to get more separation. For one project, I got the sound I was looking for by putting a 4 x 12 cabinet flat on its back, then draping blankets, sleeping bags and duvets directly over the cabinet and microphone stand.
Yet another approach, which has been used on many records, is to have the guitarists playing in the same room as the rest of the band, monitoring via headphones in the usual way, but with the amp miked up in a separate room, or even in a cupboard. Many a classic album has been recorded with the guitar amp in the studio toilet!
Because guitar amps are traditionally miked very close to the speaker grille, spill from other amplifiers or from drums should be at such a low level as not to be a problem. However, whenever you're recording multiple sources at once, using a separate mic for each source, you should always observe the 5:1 rule. That is, you should always ensure that the microphones are separated from each other by at least five times the distance between the microphones and the sources they are recording. This helps avoid phase-cancellation coloration, which is caused by the same source being picked up strongly by two or more microphones.
Where everyone is playing in the same room, a practical setup is to have the players arranged in a horseshoe shape, with the singer in the centre facing the drummer, and the amplifiers facing outwards, screened as well as possible. Remember that using improvised sound absorbers to provide separation and to deaden room coloration is essential for optimum sound quality, so don't skimp in this vital area.
With the exception of the rattling snare drum problem mentioned earlier, close-miked drums don't suffer too much from spill, as drums are basically loud and the mic is usually very close to the drum head. The room acoustics also have little influence on either close-mic'd drums or close-mic'd electric guitar amplifiers, simply because of the proximity of the microphone to the sound source. The overheads are, however, rather more vulnerable, as they are further from the kit and consequently likely to pick up more spill and room ambience. A useful strategy here is to position the overheads slightly in front of the kit and lower them to just above cymbal level. Try to position them so they are not too close to or far away from any individual cymbal, and aim the mics down towards the snare drum, trying to keep them both the same distance from the snare drum if possible. Hanging a duvet or other acoustic absorber behind the kit can stop the overheads picking up reflections from the rear wall and, if at all possible, it is worth using foam collars (such as those made by Auralex) or SE's Instrument Reflexion Filters directly behind the mics, to reduce the impact of sound approaching from the rear and sides of the mics. Even cardioids are only 'deaf' to sound directly on the rear axis — sounds coming from the sides are picked up relatively strongly. If you can improvise more substantial acoustic absorbers between the overhead mics and the guitar amplifiers, so much the better. However, remember that eye contact is often an important part of a good performance, so make sure the drummer can still see the other band members.
If you're still suffering more spill than you'd like when you come to mix, you may need to rely a little more on the close mics, and a little less on the overheads. However, the overheads do need to be loud enough to provide a credible balance for the cymbals, so a useful compromise is to apply some low cut to the overheads at around 250Hz, to clean up the sound and focus on the cymbal component. When this signal is added to those from the close mics, you should still get all the punch you need, but without the muddying effect produced by all that low-frequency and lower-mid spill.
Because I've assumed that this recording is being made in a typical home studio environment, where the acoustics are unlikely to be conducive to a great drum sound, you will need to add in some artificial ambience using a reverb device or plug-in of some kind. Short ambience treatments work well to provide a sense of space without making the sound seem too muddy or washy. This approach can be very successful, providing you've used acoustic absorbers to reduce the amount of off-axis sound getting into the overhead mics, as adding artificial reverb to unpleasant room coloration rarely works. Also bear in mind that any compression you add to the overhead mics will also emphasise spill and room coloration, so if you need to create a punchier sound it may be safer to apply compression mainly to the close drum mics, rather than to the overheads or the overall drum mix. Overall EQ lift in the 12kHz region will add sparkle to the cymbals, and you may also find you need some lower-mid cut in the 200 to 400Hz range, to tame any boxiness that has crept into the sound due to the room acoustics.
The bass guitar itself is easy to record — either via microphone or DI — but it can cause problems elsewhere in the room, as low frequencies are not so easily contained as mid-range and high frequencies. Low bass also tends to cause snare-drum vibration problems. One compromise is to simply play the bass at a lower volume, which shouldn't affect the feel of the performance if everyone hears a decent headphone balance. Another useful tactic is to record the output of the bass amp, either via a mic or by DI'ing from the preamp, but at the same time to record a clean DI directly from the bass itself, using an active DI box to split the signal. You can then EQ out some of the low bass from the amplifier to reduce drum rattling, adding this back in when you mix from the direct (non-EQ'd) DI. The thinking behind this is that most of the character of a bass sound resides in the mid-range frequencies, so it shouldn't make the sound any less characterful if you exclude the deep bass from the amp and then replace it with the low-pass-filtered direct DI.
Of course, you can lose the spill altogether by using a recording preamp such as Line 6's Bass Pod, which will give a good account of itself for just about any musical style, but don't forget that you need to have a good headphone mix set up to recreate the experience of playing at a realistic level.
If there's an acoustic guitar in the band, you can pretty much forget about recording it with a microphone in the same room as the amps and drums, as the spill will massively outweigh what you pick up from the guitar itself. The only practical choices when working in a small project studio are to use a pickup of some kind to DI the guitar, have the guitar played at the same time but in a different room, using suitable monitoring, or to overdub the acoustic guitar after the main recording has been made. This last option can be problematic if the acoustic guitar plays any solo sections, as matching up the timing can be difficult (if not impossible) so, in songs where the acoustic guitar plays a pivotal part, either recording via a pickup, or recording in a separate acoustic space provide the most pragmatic solutions. A useful tip here is that if you're not entirely satisfied with the sound of the DI'd acoustic guitar you can improve it by using a Fishman Aura preamp (or similar device), which modifies the spectrum and adds back missing body resonances to try to make the DI'd sound appear more like what you'd expect to hear if you'd mic'd the instrument. You can achieve something similar without hardware by using a 'fingerprint EQ' plug-in, such as Logic Pro's Match EQ or TC Electronic's Assimilator for Powercore. These require you to make a short recording of the instrument via a properly set-up microphone, to act as a reference. The plug-in then computes a complex EQ curve that matches the DI'd sound to the reference sample recording.
As with acoustic guitar, the human voice versus a 100W Marshall stack is a no-contest scenario, so to have any chance of recording usable vocals at the same time as the other instruments, you need either to moderate the sound levels in the room or move the singer to an adjoining room. The latter is preferable from the separation point of view, but less than ideal from a performance perspective. Most often, the singer will record a guide vocal in the room with the band and then replace this later as an overdub but, where it is imperative that the performance be captured live, a substantial expanse of duvet behind the singer and an SE Reflexion filter or similar screen behind and to the sides of the mic will help a lot. Providing the amps are pointing away from the vocal mic, and that the singer works very close to the mic, as they would in live performance, you might just get away with it. Working this close invariably means using either a stage dynamic mic, normally designed for hand-held use, or a stage hand-held capacitor mic, such as the Neumann KMS105 or the Rode S2. If you use a conventional side-address studio microphone you're unlikely to be able to get close enough to eliminate the worst of the spill without serious popping problems, as any effective pop screen needs to be located a couple of inches from the mic to be effective. Even using a stage mic you'll probably still need good mic technique to avoid popping and, if at all possible, you should get the singer to leave the mic on the stand rather than holding it, as the relative position of the mic and acoustic screens is important.
As with any recording session, remember to consult the singer as to what headphone monitor balance they need and how much reverb they'd like to hear on their own voice while performing.
Keyboards can usually be DI'd without causing any problems, unless you're miking a real rotary speaker cabinet — not a common occurrence in project studios, due to the large physical size of the things! In the event you do have an old Leslie lying around that you wish to use for the recording, there's no reason not to DI the keyboard dry, then feed the track back out through the Leslie prior to mixing, recording the result onto a new stereo track.
Brass and woodwind instruments are generally fairly loud, and a rock sax sound can be achieved by miking close to the bell, even though this doesn't give the most accurate representation of the instrument. Again, relative position of the mic to the instrument is important, and clip-on mics can be useful here if the player tends to move around a lot. In terms of separation, you can apply the same rules when recording quieter wind instruments as when recording vocals — that is, putting absorbers behind both the player and the mic.
Acoustic pianos can be a problem, but in a rock band context you're unlikely to be trying to create a classical concert piano sound, so you can afford to use a pair of mics just a few inches from the strings. If there's enough room, you may even be able to close the piano lid to give you better isolation. This will produce a harder, more assertive sound than classical miking at a distance, but many pop and rock producers prefer this sound in any case, as it cuts through well in a mix. The simplest solution, of course, is to use a good electronic piano, but not every player is happy to make that compromise.
In my experience, a lot of bands try to play their studio set just as they would live, which often results in a guitar tone that is far too dirty to mix comfortably. A practical solution is to use an active DI box to split the guitar signal, so that the Thru signal feeds the amp and the buffered signal is recorded clean to a separate track. If you find the original mic'd amp sound isn't working in the mix, you then have the option of re-amping the clean DI'd track by feeding it out into a guitar amp that has been mic'd in the usual way, or using a plug-in amp simulator to turn the DI'd sound into a plausible rock sound. You may even be able to combine the processed DI'd sound with the original amp recording to achieve a satisfactory result. If you're not convinced the band has got it right, this is a very easy way to cover yourself.
On the subject of setting levels, you should remember to leave plenty of headroom, as sound levels invariably creep up as the players get into their stride during the session. If you are recording at 24-bit resolution, then you can easily afford to leave 12dB of headroom, which will normally give you a viable safety margin against 'level-creep'.
Most of what I've discussed here would seem, in hindsight, to be largely common sense, but it is surprising how many seemingly obvious factors can get overlooked when your prime concern is getting your music down. Moderating the level of guitar and bass amplifiers, either by choosing smaller amplifiers or using power soaks, not only reduces spill but often produces a better sound. Recording with less amplifier distortion than you use live is also a good thing to try if you can: you can always add more distortion or compression later, but you can't clean up a sound that has been over-distorted, which is why I suggested the 'safety' straight DI.
The other important factor is the use of acoustic screens (or mattresses, duvets, sleeping bags and so on). These make a huge difference in minimising spill and taming unwanted room reflections, and you should not under-estimate their importance. The new generation of screens designed to go behind mics are also very effective, and if you do a lot of recording as a band, these are well worth considering. However, you should always remember to balance the use of screens with the need for visual communication between the members of the band while performing.
Finally, the better your source sounds, and the less spill you have, the easier your song will be to mix. By now you will probably have learned that the phrase 'fix it in the mix' is somewhat over-optimistic and that a great mix starts with a great recording of a great performance.